The recA protein has dual functions in bacteria leading to the development of antibiotic resistance, which makes it an ideal target for slowing the incidence of drug resistant pathogens. First, RecA induces the cellular SOS system in response to DNA damage, which can lead to error-prone DNA repair and advantageous protein mutations to escape the antibiotic challenge. Second, RecA catalyzes homologous recombination, which can spread resistance genes from organism to organism. In both instances, RecA is active as a nucleoprotein filament in which multiple monomers are polymerized head to tail along single- stranded DNA. We aim to inhibit RecA with structured peptides that mimic the dimerization interface, and with peptide nucleic acids (PNAs) designed to inhibit RecA translation through antisense interference. To these ends, our first designed peptide inhibitor has an IC50 of 3 mu M. Under this funding, interfacial residues will be randomized Using phage display techniques to improve the binding and specificity. Several antisense PNAs have been designed and will be tested for their in vitro inhibition of translation. Both peptide and PNA systems will be tested for in vivo activity in E. coli using either biotin or peptide translocation tags.